A man buried up to his chest by an avalanche of dry cement at an industrial plant was in serious condition Friday after firefighters extracted him from a mound of gray powder, officials said.

The 29-year-old worker, whose name was not released, was operating a front-loader at a ground-level opening of a dome-shaped reservoir when dry cement rushed down, burying him and knocking over the vehicle, Fire Department spokeswoman Dana Vander Houwen said.

Rescue crews were able to extract the man about 1 1/2 hours after they reached the south Seattle plant.

The man remained alert and conscious during the rescue, even using a shovel at one point to help the crew of firefighters trying to rescue him, Vander Houwen said. Firefighters also gave him oxygen during the rescue. No other worker was injured.

He was taken to Harborview Medical Center, where a nursing supervisor said he was admitted in serious condition.

Ash Grove officials said they were working with authorities to determine the cause of the avalanche.